000 AXPZ20 KNHC 180220 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sun Jun 18 2017 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 0000 UTC surface analysis and satellite imagery through 0215 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends NW across the Gulf of Panama from 09N78.5W to the Pacific coast of Costa Rica at 12N87W to 14N100W, then turns SW to 10N124W where scatterometer winds indicate that the ITCZ forms and continues SW to beyond 08N140W. Scattered moderate isolated strong convection is observed mainly to the S of the monsoon trough within 120 nm either side of a line from 06N80W to 08N88W to 13N97W to 08N118W to 10N130W. Broad surface low pressure is forecast to continue for the next few days across most of Central America and Eastern Mexico under a diffluent upper ridge. Additionally, a surface low over the Gulf of Honduras is expected to drift NW across the Yucatan Peninsula during the remainder of the weekend, and into the S- Central Gulf of Mexico early next week where tropical cyclone formation is likely. Locally heavy rainfall accumulations are possible as large clusters of TSTMS develop. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A nw to se orientated ridge will meander across the EPAC waters well to the W of the offshore zones through Wed night, while a NW to SE orientated trough will meander E to W across the Baja Peninsula and Gulf of California. A gentle to locally moderate NW breeze is forecast across the offshore waters W of 112W through Sun evening, then the pressure gradient will tighten with the NW flow increasing to a moderate to locally fresh NW breeze that will persist through late Mon, with these conditions continuing to the W of 113W on Tue and Wed as a N to S trough develops along 112W. Strong northerly drainage winds are expected in the Gulf of Tehuantepec on Mon night into Tue, and strong to near gale force northerly flow is forecast on Tue night into Wed. Large SW swell is forecast across the waters S of 13N beginning on Sun night. A moderate W to NW breeze is expected elsewhere across the open Pacific waters through early Mon when the flow will diminish to a gentle westerly breeze. Large NW swell will reach 30N120W on Tue and reach 25N118W on Wed and Thu. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Broad low pressure is forecast across Central America and the adjacent offshore waters for the next few days. A moderate to locally fresh SW to W breeze is expected to dominate the entire forecast area through Mon, then the pressure gradient will relax with a gentle to moderate SW breeze forecast to continue through Thu night. Long period SW swell will build seas to 6 to 9 ft across the waters S of 02N through late tonight, and across the entire offshore waters by late Sun. These seas will begin to subside from the N on Sun night, with seas less than 8 ft everywhere by Wed evening. REMAINDER OF THE AREA... An area of 6 to 9 ft seas, primarily due to SW swell, is currently observed to the S of 06N E of 125W. These seas will continue to propagate NE covering the waters S of 15N E of 120W early this week. Expect 3 to 6 ft seas to the lee of the Galapagos Islands. These seas will begin to subside from the N on Sun night. A quasi-stationary surface high is centered just N of the area near 34N136W with a ridge extending S-SE to near 11N120W. This ridge will gradually shift westward over the next few days terminating near 11N124W on Mon night. The ridge axis is forecast to move W of 140W by mid week. A surface trough will extend S from the Baja California Peninsula to 17N114W on Mon night, and then shift W on Tue with a surface low developing along the trough near 20N116W on Wed. The low should reach near 19N120W on Thu night. The will result in the pressure gradient tightening this week, with fresh N winds across the waters N of 29N between 124W and 132W on Mon. These fresh N-NE winds will spread SW across the waters N of 25N W of 120W on Tue and Wed, with large N swell building seas to 8 to 12 Ft to the N of 20N W of 120W on Thu. $$ Nelson